In color photography, as is generally known a color image is formed in the color development process of a silver halide color photographic light-sensitive material, during which an oxidized aromatic primary amine type color developing agent couples to a coupler so as to produce a dye such as indophenol, indoaniline, azomethine, phenoxazone, quinoneimine, phenadine, and the like. In this case, a color subtraction process is generally used for color reproduction, in which the couplers forming a yellow, magenta, or cyan dye which are in the complementary color relation to the silver halide emulsions selectively sensitive to blue, green, or red, respectively. For example, as the yellow couplers forming yellow dyes, a compound having an open-chained active methylene group is generally used. As the magenta coupler forming magneta dyes, a pyrazolone, pyrazolobenzimidazole, pyrazolotriazole, or indazolone type compound is used. And, as the cyan couplers forming cyan dyes, a compound having a phenol or naphthol type hydroxyl group is used.
In general, such color couplers require reduction of 4 silver atoms to produce every one molecule of such a dye. From the viewpoint of the shortage of silver resources, a silver-saving type color coupler has been proposed. For example, as proposed in Japanese Patent Examined Publication No. 49-13576(1974), there is a well known technique using a so-called 2-equivalent type color coupler introduced a split off group into the active site thereof so that one molecule of a dye can be produced with reduction of 2 silver atoms. According to this technique, an amount of silver used may be saved by half as compared to that of a so-called 4-equivalent type coupler in conventional use. In recent years, therefore, the 2-equivalent type couplers have popularly been used.
However, there have been still demanded to further improve the characteristics of the well-known 2-equivalent type coupler, though the characteristics of the couplers are acceptable to some extent. In particular, the color forming efficiency is not satisfactory. Therefore, a highly reactive coupler has been demanded from the standpoints of making sensitivity and image quality higher and making processing time shorter, at which have strongly been aimed in recent years. In other words, the sensitivity of a light-sensitive material can be improved by enhancing the reactivity of a coupler to be reacted with the oxidized product of a developing agent. The amounts of both couplers and silver halide can be reduced as much as the amounts thereof to be used to make the sensitivity of the light-sensitive material higher by enhancing the reactivity of the couplers, provided, such high sensitization is not desired. The improvements described above will result in the improvement of image sharpness, because the layer thickness of the light-sensitive material can be reduced so that the scattering of incident light can also be reduced. In the case of both color negative and color reversal light-sensitive materials, it is most effective in improving them to reduce the thickness of the blue-sensitive layer thereof because the blue-sensitive layer thereof is closest to the side of incident light. Therefore, it has particularly been expected to develop highly reactive yellow couplers.
On the other hand, from the aspect of development processes, benzyl alcohol has been added to the conventional type developer to enhance the color develpment efficieny of a light-sensitive material. However, benzyl alcohol has the problems of environmental pollution such as an increase of B.O.D. which stands for biological oxygen demands. In the course of a color development process, it has therefore been required to reduce an amount of benzyl alcohol used therein. On the contrary, when reducing benzyl alcohol from the developer, particularly, when making a processing time shorter, there raised a problem that a color density is seriously lowered in photograpic materials using the conventional color coupler. It has therefore been seriously demanded to develop a yellow coupler having a satisfactory color forming efficiency.
From among the conventional types of 4- and 2-equivalent yellow couplers, nothing has been found out to satisfy both of the above-mentioned problems. Apart therefrom, a 2-equivalent type yellow coupler having an aryloxy group as the split-off group thereof has attracted the general attention as a coupler satisfying both of the above-mentioned problems. For example, U.S. Pat. No. 3,644,498 discloses an aryloxygroup split-off type 2-equivalent yellow coupler having a sulfamoyl or acylamino group as the ballast group thereof; Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) No. 59-174839(1984) discloses an aryloxy group split-off type 2-equivalent yellow coupler having an alkoxycarbonyl group as the ballast grou thereof: and Japanese Patent O.P.I. Publication No. 60-69653(1985) discloses an aryloxy group split-off type Z-equivalent yellow coupler having an alkyl or arylsulfamoyl group as the ballast group thereof. It has been proved that the above-given couplers can remarkably improve a color forming efficiency, particularly when introducing into the p-position of the aryloxy split-off group with such a so-called electron attractive group as a sulfonyl, sulfamoyl, carbamoyl, acyl, formyl, nitro, or cyano group. However, these couplers have had the problems that they do not fully satisfy the dissolving property to a high boiling organic solvent, due to the influence of the ballast group contained therein, and that they have had a substantially low dispersion stability in a silver halide emulsion. These facts have further proved to be more serious particularly when reducing a content of the high boiling solvent to thin the layers of a light-sensitive material so that the recent strong intention to thinned layers may be satisfied. In addition to the above, most of the couplers disclosed in the above-given patent specifications still have the problems that an amount of such couplers coated should be increased because of an unsatisfactory coupling reactivity, a low color density, and the like. A further improvement of the couplers has therefore been desired.
As the aryloxy group split-off type 2-equivalent yellow couplers further improved both of the dissolving property to a high boiling solvent and a color forming efficiency, Japanese Patent O.P.I. Publication Nos. 62-153954(1987) and 63-43144(1988) disclose the compounds having an alkyl or an arylsulfonamido group as the ballast group thereof. These couplers are the compounds with the purpose of improving an image preservability and it can still hardly be said that the color forming efficiency is satisfactory. Besides, Japanese Patent O.P.I. Publication No. 62-153955 (1987) discloses the aryloxy group split-off type 2-equivalent yellow couplers each having a peculiar arylsulfonamido group as the ballast group thereof. Even with these couplers, it cannot be said that the demands for a high dissolving property to a high boiling solvent and a high color forming efficiency can be fully satisfied and, furthermore, these couplers have another problem that the ballast group thereof is so complicated that the production costs should be increased.
U.S. Pat. No. 4,401,752, and Japanese Patent O.P.I. Publication Nos. 59-228649(1984), 62-204259(1987), and 62-250446(1987), each disclose that a color forming efficiency may further be improved particularly when introducing a substituent bonded to a hetero atom into the o-position of an aryloxy split-off group. Among these patent specifications, Japanese Patent O.P.I. Publication No. 62-204259(1987), and 62-250446(1987), each disclose the yellow couplers each having a carbamoyl group as the ballast group thereof and a substituent bonded to a hetero atom at the o-position.
However, the introduction of a substituent into a o-position of an aryloxy split-off group will result in the deteriorations in both dissolving property to a high boiling solvent and a dispersion stability in an emulsion. These couplers have therefore been unable to solve the above-mentioned conventional problems successfully.